The present invention is directed to a machine tool having a compartment containing lubricant and a device for compensation of the pressure in the compartment according to the definition of the species in claim 1.
A machine tool forming the species, in particular a hand-operated hammer drill, is known from German Patent 42 31,987.0 A1. The hammer drill has a drive motor, arranged within a motor compartment of a housing, having a motor shaft that extends through a housing section into a gear compartment, where it engages, via an integral pinion, with a gear wheel of a gear unit for driving a tool-holding fixture. The gear compartment is provided with a pressure-compensation device that reduces a pressure, resulting during operation within the gear compartment, down to that of the atmosphere or of the motor compartment. The pressure-compensation device has a pressure-compensation channel leading from the gear compartment to the outside, or to the motor compartment, implemented as a bore hole, that is introduced into a housing part.
The pressure-compensation channel is shielded by a rotary element or centrifugal component, rotationally mounted in the gear compartment on a pin that is integrally formed on the housing part. The rotary element is formed by a pot-shaped sheet-metal part into which a passage is introduced. The rotary element is operably connected to the gear wheel of the gear unit that is driven via the pinion, and specifically via a compression spring whose ends engage the gear wheel, on the one side, by form-fitting connection and the rotary element, on the other side, by frictional connection. The compression spring transfers the rotary movement of the gear wheel to the rotary element.
The present invention is directed to a machine tool, in particular to a hand-operated hammer drill, having a compartment containing lubricant in which at least one rotationally drivable component is mounted, and having a device for compensating the pressure in the compartment, the device having a rotationally drivable centrifugal component that shields at least one a pressure-compensation channel disposed downstream from it, in terms of fluid mechanics, in the venting direction of the compartment.
It is proposed that the centrifugal component be mounted in a torsionally fixed manner on the rotationally drivable component. It is possible to avoid additional components driving the centrifugal component, thereby saving space, weight, assembly effort and costs. If the rotationally drivable component is formed by a shaft, and if the centrifugal component adjoins a transmission means mounted on the shaft and extending in a radial direction, for example a gear wheel, a bevel gear of an infinitely variable gear unit, a V-belt pulley, etc., a large radial distance between an outer diameter of the centrifugal component and the pressure-compensation channel may be beneficially achieved using few additional components, thereby achieving a beneficial shielding effect. Furthermore, a long pressure-compensation channel, and an associated beneficial labyrinth and sealing effect, is attainable using a simple design. However, it is also conceivable, in principle, for the centrifugal component to be adjacent to a component separate from the transmission means, for example, a partition wall of a housing or a component additionally provided for this, etc.
It is proposed in another embodiment of the present invention, it is proposed that the centrifugal component be formed of a disk that extends axially toward the transmission means, conically radially to the outside. A beneficial shielding effect may thereby be achieved, and this is the case in particular, if the centrifugal component is positioned upstream of the transmission means, in terms of fluid mechanics, in the venting direction of the compartment.
If, in the radially outer area of the centrifugal component designed as a disk, at least one recess forming a pressure-compensation channel is placed in the centrifugal component and/or in the transmission means, a desired flow cross-section may be simply and deliberately set, via which pressure is intended to be equalized. Furthermore, it is possible to ensure that lubricant that has gotten into a space bordered by the centrifugal component and the transmission means is able to flow back. However, it is also possible for the centrifugal component to adjoin the transmission means with small clearance, so that between the transmission means and the centrifugal component, a groove seal is formed via which pressure may be compensated, but which at least substantially prevents lubricant from escaping from the compartment.
Furthermore, the shielded pressure-compensation channel is beneficially formed at least partially by a threaded depression, which, except for an inlet, shielded by the centrifugal component, in the compartment, is covered in a lubricant-tight manner. A beneficial labyrinth effect or labyrinth sealing may be achieved, and a recirculating effect as well; and specifically, by coordinating the threading and rotational directions accordingly. The threaded depression may be introduced into one or more components mounted on the rotationally drivable component, for example, in the transmission means, in a bearing ring of a bearing of the rotationally drivable component, etc. However, the threaded depression is advantageously introduced into the rotationally drivable component designed as a shaft. The depression may beneficially be placed in a component in one processing step, and the depression may advantageously be covered, at least substantially in a lubricant-tight manner, depending on the centrifugal component, using already existing components. If the pressure-compensation channel opens through into at least one annular groove, it can be produced especially simply and economically, for example, in one lathe operation, starting from a first annular groove and opening through into a second annular groove or at an end face.
In another embodiment of the present invention, it is proposed to position a sealing ring that seals the depression in the radial direction, between the transmission means and a bearing of the rotationally drivable component. Starting from the centrifugal component, a threaded depression introduced into the rotationally drivable component, designed as a shaft, may be advantageously covered in a lubricant-tight manner by the transmission means, by the sealing ring and by the bearing. Furthermore, the sealing ring may also be used to seal the compartment outwardly, in the area of the bearing, in a lubricant-tight manner. Overall, therefore, except for the centrifugal component, the need is eliminated for additional components for the pressure-compensation device.
The approach of the present invention is applicable to all machine tools deemed suitable by one skilled in the art, in particular in hand-operated machine tools, such as, grinders, saws, milling cutters, planers, drills, chisel hammers, etc.